Tuberous sclerosis complex (TSC) is a genetic disease characterized by hamartoma formations in a wide range of tissues. Mutation in either the TSC1 or TSC2 tumor suppressor gene is responsible for TSC. TSC1 and TSC2 play a major role in the regulation of cell growth and cell size through control of protein synthesis. The TSC1/TSC2 complex functions upstream of the mammalian target of rapamycin (mTOR) and inhibits mTOR function. These observations suggest that TSC1/TSC2 are key regulators of cell growth and tumor formation. Protein synthesis is regulated by multiple intracellular and extracellular signals, such as mitogenic growth factors, nutrient sufficiency, and cellular energy levels. Cellular energy starvation results in inhibition of both protein synthesis and cell growth. However, the molecular mechanisms coordinating cellular energy level and cell growth is not well understood. Recent studies from our laboratory have indicated that TSC2 plays a major role in coordinating cellular energy levels and cell growth. The major goal of this proposal is to study the function and regulation of TSC2 in the cellular energy response. Completion of this proposal will address the fundamental cell biology question of the coordination between cell growth and cellular energy levels and will provide an exciting mechanism of how multiple signaling pathways are integrated at the molecular level. Results from this project will reveal a molecular basis for tumorigenesis induced by disregulation of the Wnt pathway. The following specific aims will be addressed. 1. To determine the function of GSK3 and Wnt in the TSC-mTOR-S6K pathway. 2. To determine whether AMPK and GSK3 collaboratively phosphorylate and regulate TSC2 under energy starvation conditions. 3. To elucidate the physiological functions of TSC2 phosphorylation by AMPK and GSK3 in cellular energy response. 4. To investigate the mechanism of TSC2 in energy starvation-induced cell death.